I had created an experiment in which trials contained a pattern of fixed and random events that followed a rule similar to "1R2R3R4R". Here the numbers represent the sequence events that were pulled from a stimulus list in a sequential order (1234) and by using the "unpaired" condition at the trial level, events were pulled from a second stimulus list in random order. Each stimulus from each list event list was in the form of a picture.

In the experiment, the presentation of this sequence-random pattern was repeated 10 times (using 10 trials) in one block. The experiment consisted of 20 blocks, which would amount to 20,000 events presented.

The presentation of the 10-element sequence-random pattern "1R2R3R4R2R"(for example) across 10 trials works perfectly within one block. However, when the experiment progresses automatically to the second block, which is designed to be exactly the same as the first, the trial rules are not followed and all events are presented at random. This continues for all consecutive blocks in the experiment.

What's most strange about this is that when any of the 20 blocks are run on their own, the sequence-random rule is followed. It just doesn't seem to work for 2 or more consecutive blocks.

Your insights and ideas of what could be causing this or can resolve it would be greatly appreciated!